Spatial light modulators (SLMs) are commonly used for image display applications. In general, an SLM is an array of individually addressable pixels. Many SLMs are binary, having an address scheme that switches the pixels to either to an "on" or an "off" state to form the image. Various modulation and integration schemes are used to provide greyscale images.
One type of SLM is a digital micro-mirror device (DMD), sometimes referred to as a deformable mirror device. The DMD has an array of hundreds or thousands of tiny tilting mirrors, which are the pixels. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by means of an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. For display applications, image data is loaded to the DMD, and in accordance with the data, light is selectively reflected or not reflected from each mirror to an image plane.
For display systems that are based on SLMs, a conventional method for increasing resolution of the image is to increase the number of pixels in the SLM array. Thus, for increased horizontal resolution, more samples of data per row are generated and an SLM having more pixels per row is used. For increased vertical resolution, more rows of data are generated and an SLM having more rows per image is used. A drawback of this approach is that the SLM is more complex, and therefore more expensive. Also, unless the size of the pixels of the SLM is adjusted, an increase in the number of pixels per row without the proportionate increase in the number of rows, or vice versa, will alter the aspect ratio of the output image.